/Engine/Source/Runtime/SlateCore/Public/Layout/Geometry.h
Makes a new geometry that is essentially the root of a hierarchy (has no parent transforms to inherit). For a root Widget, the LayoutTransform is often the window DPI scale + window offset.
The new root geometry
static [FGeometry](API\Runtime\SlateCore\Layout\FGeometry) MakeRoot ( const [UE::Slate::FDeprecateVector2DParameter](API\Runtime\SlateCore\Types\FDeprecateVector2DParameter) & InLocalSize, const [FSlateLayoutTransform](API\Runtime\SlateCore\Rendering\FSlateLayoutTransform) & LayoutTransform )